The present invention relates to a sintered polycrystalline diamond composite for use in rock drilling, machining of wear resistant materials, and other operations which require the high abrasion resistance or wear resistance of a diamond surface. Specifically, this invention relates to such composite bodies which comprise a polycrystalline diamond layer attached to a cemented metal carbide substrate via processing at ultrahigh pressures and temperatures.
It is well known to sinter a mass of crystalline particles such as diamond or cubic boron nitride in the presence of a suitable solvent catalyst by means of a high pressure, high temperature apparatus to form a compact with good particle-to-particle bonding. Typically the diamond is a synthetic industrial grade diamond with a nitrogen content above 1000 ppm. It is also well known that use of diamond particles smaller in size result in a compact with higher abrasion resistance when used to machine or drill certain materials such as rock. However, there is a limit as to how fine a particle size becomes useful since the impact strength and thermal stability of a compact are reduced as the diamond particle size becomes smaller. Such composite compacts are widely used in machining and drilling since the carbide substrate provides good mechanical support and can be clamped or brazed to a suitable tool holder or drilling bit.
It would be useful if the wear life of a compact could be extended without giving up impact resistance as happens with smaller diamond particle size or by having to make the diamond layer thicker which increases the stress in the compact leading to early catastrophic failure due to cracking or delmination.